A 50% solution of sodium hydroxide (100 ml) was added to a vigorously stirred solution of indole (5.8 g, 50 mmol) and tetrabutylammonium hydroxide (40% by weight solution, 2 ml, 3.1 mmol) in tetrahydrofuran (100 ml). After 5 minutes, a solution of 2-acetyl-1,2,3,4-tetrahydroisoquinoline-7-sulfonyl chloride (R. G. Pendleton et al., J. Pharmacol. Exp. Ther., 1979, 208, 24; U.S. Pat. No. 3,725,388 (1973)) (13.7 g, 50 mmol) in tetrahydrofuran (50 ml) was added over 10 minutes and the resulting mixture was vigorously stirred for a further 3 h. The mixture was then extracted with ethyl acetate (250 ml) and the extract dried (MgSO4), concentrated in vacuo and the residue purified by column chromatography over silica gel eluting with a dichloromethane/methanol gradient to give the title compound (D1) (12.8 g, 72%), NMR (CDCl3; rotamers observed)/ppm 2.12, 2.14 (3H, 2×s), 2.77-2.88 (2H, m), 3.60, 3.74 (3H, 2×t J=7 Hz), 4.59, 4.68 (2H, 2×s), 6.65-6.67 (1H, m), 7.16-7.34 (3H, m), 7.50-7.69 (4H, m), 7.94-7.99 (1H, m); MS: m/z (MH+) 355.
